The present invention includes a positioning apparatus for use with transversal dental x-ray tomography. More particularly, the invention relates to a device which employs a dental impression held within an impression tray, and which aligns an x-ray shot by use of the impression.
Dental x-ray transversal tomography or scanography, is a projection modality provided by modern dental panoramic x-ray equipment for imaging the jaw in the transverse direction. Such images in the dental practice by using panoramic x-ray equipment is useful, especially in implantology, and compares with the tomographic imaging which can be obtained with much more complex and expensive tomographic equipment.
In combination with such imaging by using panoramic x-ray equipment, it is extremely important to provide an accurate and reproducible positioning of the patient. Transversal tomography equipment is capable of producing precise and accurate x-ray images. However, it has been found that it is often difficult to properly align the patient to take full advantage of the potential precision of the x-ray apparatus.
A method of aligning a patient is disclosed for example, in U.S. Pat. No. 5,444,754. The method includes imaging cross-sections on the same film as a respective longitudinal image of the dental arch. The cross-sectional images are exposed to include identifications for the sections. U.S. Pat. No. 5,431,162 employs a stent aligned with the imaging device so that a mark on the stent is aligned with a light beam. This patent also describes an exemplary x-ray machine, which disclosure is hereby incorporated by reference.
A need exists for an improved apparatus and method for properly aligning a patient when taking a transversal tomography x-ray image. The apparatus and method should naturally include ease of use and comfort to the patient.
It is therefore, an object of the invention to provide an apparatus and method for transversal dental x-ray tomography, allowing off-line alignment of the patient denture impression with respect to the biting point of a panoramic x-ray equipment, and accurate and reproducible patient positioning on-the-equipment during the imaging process.
The apparatus is a mechanical alignment device comprehending supports and joints, and is based on the following components and features:
A support tray, over which standard impression material is hardened to provide the reproduction of the patient denture at the occlusal plane.
The tray can either be a standard commercially available dental tray for impression, or a custom made tray for this application.
A positioner, holding the tray with denture impression, and fitting into the bite block holder of the panoramic x-ray equipment. The positioner is provided with slides and joints, allowing off-line free adjustments of the denture impression support: linear movement in the X and Y direction, rotation around X and Z axis.
A graduated scale in mm and degrees is provided for each adjustment movement. Transparent guide plates with silk screen reference of the target sections and teeth icons, allowing positioning of the region of interest with respect to the same target sections.
The first transparent plate is dedicated to the upper dentition, the second to the lower dentition.
A workbench support, provided with base, column and fastening screw, on which the positioner is mounted during the off-line adjustment phase.
The positioner is mounted upside for upper jaw and downside for lower jaw.
The method is articulated in several steps as follows:
(1) The patient bites the impression material to reproduce the denture occlusal plane (upper or lower jaw, using different denture support). A marker (steel ball or guttapercha cone) can be introduced into the impression, in correspondence with the region of interest.
(2) The positioner is placed on the workbench (upside for upper jaw, reversed for lower jaw), and the tray is mounted on the positioner.
(3) For upper jaw the tray is adjusted perfectly in the horizontal plane, for lower jaw a slight adjustment of the tray below the horizontal plane is allowed.
(4) The transparent guide plate is mounted on the positioner.
(5) The tooth icon is aligned with the diagnostic target zone on the impression, by using the vernier slides (X, Y axis) and the rotation around the Z axis.
(6) The tray position is fixed by securing the corresponding fastening screws.
(7) The panoramic x-ray equipment is prepared for transversal tomography.
(8) The positioner with the support tray is mounted on the bite point of the panoramic x-ray equipment.
(9) The patient is invited to bite into the impression to ensure a firm positioning, and then the imaging process is started.
The apparatus is designed to accommodate critical patient morphology, as derived by anatomical studies extended to patients of various race, age, and sex.
These and other objects of the invention, which will become apparent from the following description, are carried out by the invention as hereinafter described.